Effects of water and nitrogen coupling on strawberry yield and quality under partial root-zone irrigation

The effect of water and nitrogen application on efficient utilization of water and fertilizer under partial root-zone irrigation has attracted the attention of scientists around the globe. In order to improve the quality and yield of strawberry along with the utilization efficiency of water and fertilizer, this study examined the effects of integrated water and nitrogen management on the yield and quality of strawberry under partial root-zone irrigation. The main objective of the study was to provide a scientific basis for highly efficient utilization of water and fertilizer of strawberry. In the experiment, two factors (water and nitrogen) were set up with three levels for each factor. The roots of strawberry were well distributed in two zones-wetting and drying zones (A/B). The relative water content of soil was 80%±5% in the wetting zone (A). For the drying zone (B), the relative water content was in three levels, which were 20%±5% (sever water stress, SS), 35%±5% (moderate water stress, MS) and 50%±5% (light water stress, LS). At the same time, nitrogen fertilizer was set at 3 levels, which were respectively 0.50 g(N)·kg^-1 (lower N, LN), 0.75 g(N)·kg^-1 (medium N, MN) and 1.00 g(N)·kg^-1 (high N, HN). The two (A and B) zones of control (CK) were 80%±5% of soil relative water content and medium nitrogen0.75 g(N)·kg^-1 fertilize rate (i.e., the conventional production mode). Based on the test data, the growth, quality and yield of strawberry under different water and nitrogen conditions were analyzed and evaluated using Principal Component Analysis (CPA) and polynomial fitting. The main findings of the study were as follows. 1) Due to partial root-zone irrigation, water utilization significantly dropped while water use efficiency (WUE) improved during the growth period of strawberry. The rates of irrigation water under SS, MS and LS treatments were respectively 14.77 L, 16.62 L and 18.47 L per plant. Compared with the control treatment (which was 25 L·plant-1), irrigate rates for 3 treatments dropped respectively by 40.0%, 32.5% and 25.0%. Under MSMN treatment, WUE of strawberry was 13.55 g·L^-1, 47.1% higher than that under CK treatment; but the yield change was not significant. The yield of strawberry was the highest under LSMN treatment among all treatments, which increased 4.4% over that under CK treatment. 2) The contents of Vc, soluble sugar, organic acid and sugar acid ratio of strawberry fruits under MSMN treatment were respectively 63.32%, 12.48%, 3.90% and 8.31% higher than that under CK treatment. The effects of integrated water and nitrogen management on the yield, quality and WUE of strawberry indicated that the most suitable model of water and nitrogen management for the production of strawberry was 0.75 g(N)·kg^-1 nitrogen rate with relative soil water content of 80%±5% in the wet zone and 35%±5% in the dry zone (i.e., MSMN).